34 
NATURE STUDY. 
tures having well rounded bodies, although many of them are 
clothed with hairs to avoid tempting the greedy appetites of 
birds. But this insect is in effect at least a sweet fern leaf, and 
a sweet fern leaf has a very different appearance from that of 
an ordinary caterpillar. The leaf is long and narrow, with 
ONE OF NATURE’S PUZZLE PROBLEMS — FIND THE CATERPILLAR, 
many pointed teeth along each side the midrib, and of a dull 
green or brownish color, commonly having a rusty appearance. 
These peculiarities the caterpillar has copied so successfully 
that your chances of finding one of the larvae by searching the 
sweet fern branches in the field are considerably less than those 
of the person who hunts for a needle in the proverbial haystack. 
Even on a small branch on which you know the specimen is 
resting it requires sharp eyes to see it. It is one of Nature’s 
puzzle problems in which you are to find the caterpillar. 
When you succeed in distinguishing the insect from the sur¬ 
rounding leaves you should examine it closely to see in what 
ways this remarkable resemblance has been brought about. 
The first thing you are likely to notice is that each of the rings 
of which the body is made up instead of being round in outline 
as in other caterpillars is nearly triangular in cross-section. On 
each side of the median line the back of the ring has been de- 
